1. Field of the Invention
The present invention relates generally to connector assemblies having releasably mateable plug and receptacle units designed for use underwater or in other hostile environments, and is particularly concerned with a connector unit and method for downhole connectors exposed to gas for extended periods of time.
2. Related Art
There are many types of connectors for making electrical and fiber-optic cable connections in harsh environments, such as underwater or subsea electrical, optical and hybrid electrical and optical connectors which can be repeatedly mated and de-mated underwater at great ocean depths. These connectors typically consist of releasably mateable connector units or plug and receptacle units, each attached to cables or other devices intended to be joined by the connectors to form completed circuits. Each connector unit contains one or more electrical and/or optical contacts or junctions for engagement with the junctions in the other unit when the two units are mated together. To completely isolate the contacts to be joined from the ambient environment, one or both connector units house the contacts in fluid-filled, pressure-compensated chambers. The fluid may be a dielectric fluid or oil in the case of an electrical connector. The dielectric fluid is typically pressure compensated by means of a movable or flexible member, such as a piston or a flexible bladder, forming a wall of the dielectric chamber.
In oil and gas well connector applications, the plug and receptacle units of wet-mateable downhole electrical connectors are mated and de-mated at a point downhole or subsea in order to releasably connect power or signal to downhole equipment such as pumps, sensors, or the like, with the connector units oriented vertically or at an angle. One of the connector units is connected to the downhole equipment while the other connector unit is at the end of a power supply or signal communication cable. In gas well applications where the connector is exposed to gas for extended durations, the gas can permeate through the flexible bladder or the piston seals of the dielectric chamber and dissolve in the dielectric fluid. If the ambient pressure is reduced at a sufficiently high rate, the dissolved gas can come out of solution and expand. This expansion causes an increase in internal pressure in the connector, which can exceed the design limits of the pressure compensation devices such as pistons or bladders, potentially causing failure of those devices and thus electrical or optical failure of the whole connector.